1. Field of the Invention
The present invention is generally related to a steering system for a marine propulsion device and, more particularly, to a steering system which supports a hydraulic cylinder with a single pin and which facilitates removal and installation of the hydraulic cylinder into a pivot support structure which is attached to a transom of the marine vessel.
2. Description of the Related Art
Many different types of hydraulic actuated steering systems are known to those skilled in the art. Several types of steering systems are used in conjunction with sterndrive propulsion devices and outboard motors. Typically, these steering systems exert a force to cause the marine device to rotate about a generally vertical steering axis. The steering system can include a hydraulic cylinder which is provided with pressurized hydraulic fluid through the manual movement of a steering wheel or from a pump which provides pressurized hydraulic fluid that is directed to a hydraulic cylinder through the use of a spool valve which, in turn, is controlled by manual movement of a steering wheel. The former type of system is generally referred to as a hydraulic steering system and the latter is generally referred to as a power steering system. Those skilled in the art of marine propulsion systems are also familiar with manual steering systems that use cables to move the marine propulsion device about a generally vertical steering axis.
U.S. Pat. No. 3,589,326, which issued to Celli on Jun. 29, 1971, describes an inboard outboard drive. A sterndrive for a boat having an inboard engine and an outboard drive unit is described wherein the inboard driveshaft is connected to the propeller shaft by a two section power transmission shaft, the first section being connected to the engine driveshaft at one end by a first universal joint and connected to the second section by a second universal joint. The second section of the power transmission shaft inclines downwardly and rearwardly and is connected to the propeller shaft by an acute angle by two pair of bevel gears.
U.S. Pat. No. 3,599,595, which issued to James on Aug. 17, 1971, describes an outdrive for boats. The outdrive has a hydraulic pump including an eccentric ring which is rotatable to change the path of fluid flow under pressure so that the direction of drive of the motor can be easily reversed. Hydraulic fluid may be subjected to pressure with structure prior to communication thereof to the hydraulic pump. A transom bracket and sterndrive housing support are connected so as to provide pivotal movement of the sterndrive housing along two mutually perpendicular axes so that the sterndrive housing will remain in the water even when the boat negotiates a sharp turn, the transom bracket being provided with couplings to accommodate fluid flow therethrough and a fluid restraining recess to allow recirculation of cooling water through a driving engine carried by the boat.
U.S. Pat. No. 3,626,467, which issued to Mazziotti on Dec. 7, 1971, describes a marine drive. The outdrive unit is supported substantially on a four-bar linkage. One bar of the four-bar linkage is formed by spaced locations adjacent the transom of the boat on which the outdrive unit is mounted. The second and opposite bar is formed by fixed portions of the housing for the outdrive unit. Pivotal kickup and trim for the unit is provided by the other two bars of the four-bar linkage, one of these being formed in a series of universal joints joining the gear drive, drivingly connected to the marine engine, to the shafting driving the propeller for the marine outdrive unit.
U.S. Pat. No. 5,924,379, which issued to Masini et al. on Jul. 20, 1999, discloses an actuating mechanism with an improved mounting structure. The mechanism is provided with support members that extend away from the centerline of a cylinder bore, piston and actuator rod of an actuation mechanism that uses pressure to move the piston within a cylinder bore. Two support members are attached to a cylinder housing and provided with mounting holes. The two support members are spaced apart from the cylinder housing to allow external support structures to be placed between the cylinder housing and the two support members. Appropriate fasteners, such as bolts, attach each of the two support members to the external support structures in such a way that the cylinder housing can pivot about an axis extending through both bolts. Most importantly a line extending through the support bolts intersect the cylinder bore at a place between its opposing ends. This reduces the required space necessary to allow the cylinder to pivot properly.
U.S. Pat. No. 6,276,977, which issued to Treinen et al. on Aug. 21, 2001, discloses an integrated hydraulic steering actuator. The actuator is provided for an outboard motor system in which the cylinder and piston of the actuator are disposed within a cylindrical cavity inside a cylindrical portion of a swivel bracket. The piston within the cylinder of the actuator is attached to at least one rod that extends through clearance holes of a clamp bracket and is connectable to a steering arm of an outboard motor. The one or more rods attached to the piston are aligned coaxially with an axis of rotation about which the swivel bracket rotates when the outboard motor is trimmed. As a result, no relative movement occurs between the outboard motor, the rod attached to the piston of the actuator, and the swivel bracket during rotation of the outboard motor about the axis of rotation.
U.S. Pat. No. 6,454,620, which issued to Theisen et al. on Sep. 24, 2002, discloses an integrated external hydraulic trimming and steering system for an extended sterndrive transom assembly. The system is provided with a drive unit that is attachable to a transom of a marine vessel and provided with steering cylinder assemblies and trimming cylinder assemblies which are connected to a common location on a structural member, such as a gimbal ring. This arrangement improves the geometric relationship between the steering and trimming functions. In addition, the hydraulic steering system is provided with pressure relief valves that are located at the transom of the marine vessel in order to shorten the distance of the hydraulic conduits extending between the pressure relief valves and the steering cylinders.
U.S. Pat. No. 6,524,147, which issued to Hundertmark on Feb. 25, 2003, describes a power assist marine steering system. The system comprises a hydraulically actuated, unbalanced steering cylinder assembly, a pressure source, and helm that is spaced from the steering cylinder assembly. The helm includes a helm cylinder having a slave chamber fluidically coupled to a second chamber in the steering cylinder, a high pressure port fluidically coupled to the outlet of the pressure source and to a first chamber in the steering cylinder, and a return port fluidically coupled to the vent. A control valve assembly is movable between at least first and second positions to alternatively couple a control chamber in the helm cylinder to the high pressure and return ports. In order to facilitate mounting of the helm to the dash of the watercraft, the helm has only three ports, and all three ports are all located on a rear axial end of the helm cylinder.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In known hydraulic steering systems, a hydraulic cylinder is pivotally mounted to be able to pivot about a pivot axis as the piston rod of the assembly moves axially in response to the movement of a piston within the cavity of the hydraulic cylinder. As a distal end of the piston rod moves with a connected steering arm of the marine propulsion device, the pivotal movement of the cylinder is necessary because of the fixed relationship of the cylinder to a pivot support mechanism attached to the transom of the marine vessel and the distal end of the piston rod attached to the steering arm of the marine propulsion device. Known types of hydraulic steering systems use two pins to support the hydraulic cylinder for movement about its pivot axis. In certain types of marine vessel structures, it is difficult to remove, or perform maintenance on, these pivot pins because of spatial considerations caused by other components in the vicinity of the hydraulic cylinder. It would therefore be significantly beneficial if a support structure could be simplified so that it can be supported by a single pin which is preferably accessible from a position above the hydraulic cylinder.